The National Zoo announced Saturday that a team of scientists and veterinarians had artificially inseminated the zoo's female giant panda after natural breeding failed to occur.

The statement said that Mei Xiang was artificially inseminated with a combination of fresh and frozen semen taken from the zoo's male panda, Tian Tian. The fresh semen was taken earlier Saturday morning, while the frozen semen had been held since 2003.

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Scientists determined that Mei Xiang was ready to breed earlier this week after observing a rise in her urinary estrogen levels.

"We are hopeful that our breeding efforts will be successful this year, and we’re encouraged by all the behaviors and hormonal data we’ve seen so far,” Dave Wildt, head of the Center for Species Survival at the Smithsonian Conservation Biology Institute said. "We have an extremely small window of opportunity to perform the procedures, which is why we monitor behavior and hormones so closely.”

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Panda pregnancies last between 95 and 160 days. Experts say that it is impossible to determine from behaviors and hormones whether a panda is actually pregnant or not because a fetus does not begin to develop until the final weeks of gestation.

Mei Xiang gave birth to a female cub on September 16 of last year, but the cub died one week later due to lung and liver damage. Mei Xiang and Tian Tian have produced one surviving offspring, Tai Shan, who was born in 2005 and currently lives in China.

The panda habitat at the National Zoo has been closed since Tuesday, when Mei Xiang was deemed ready to breed. The zoo plans to re-open the habitat to visitors Sunday.

A photo released by the National Zoo of Saturday's insemination of Mei Xiang. For more pictures of the procedure, you can check out the National Zoo's Flickr page here.